Vat dyeing of animal fibers using esters



2,768,051 VAT nYEING oi ANIMAL FIBERS USING ESTERS William Kilby and James L. Harris, Lancaster, England, assignors to Standfast Dyers & Printers Limited No Drawing. Application May 19, 1952, Serial No. 288,762

Claims priority, application Great Britain May 25, 1951 4 Claims. (Cl. 836) This invention relates to the dyeing of wool and other animal fibres, or yarns or fabrics containing them, especially with vat and sulphur dyes. Vat and sulphur dyes are normally applied by means of alkaline solutions, especially caustic alkaline solutions, and such alkaline solutions are known to damage wool, particularly when used at high temperatures.

Known methods of applying vat, or sulphur dyes to wool rely on the use of low temperatures usually from about 18 C. to 60 C. (depending on the properties of particular dyestuff and on the kind of alkali used), and either on the use of mild alkalies or on the addition to caustic alkaline dye-baths of so-called protecting agents some of which partly neutralise the caustic alkali.

The invention relates also to methods of continuous dyeing, and in particular to a method involving the passage of the dye-impregnated material through molten metal as described in British patent specification No. 620,584 and United States application Serial No. 722,042, filed January 14, 1947, and now abandoned, and United States Patent No. 2,693,995, which is a continuationin-part of application Serial No. 722,042. The invention is inter alia applicable in general to continuous dyeing processes in which dyeing is efiected quickly in, say,

.under one minute. The invention is further, inter alia,

,applicable to continuous dyeing processes involving pas- ;sage of the dye-impregnated material through hot oil in ,order to apply heat thereto, and processes involving the steaming of impregnated fabric.

According to the present invention, we provide a method of dyeing animal fibres with dyestuffs, comprising impregnating the fibres with an alkaline aqueous liquor, heating the impregnated fibres, and reacting with the liquor an organic ester which is hydrolysed by the alkali so that acid is liberated which tends to neutralise the alkali in the fibres.

Further according to the present invention, we provide a method of dyeing animal fibres comprising dyeing the fibres at a high temperature with an alkaline aqueous liquor, and reacting with the liquor an organic ester which is slowly hydrolysed by the alkali in the dyeing operation with liberation of acid which tends to neutralise the alkali, so that the dyeing and the neutralisation of the alkali are effected over substantially the same period.

Preferably the impregnated fibres are heated to a temperature of the order of 80 C. to 100 0, although the invention is not limited to such temperature.

In further accordance with the invention, we provide a method of continuous dyeing with dyestuffs of a continuous length of material containing animal fibres, comprising passing the material through a bath of alkaline aqueous liquor, passing the liquor-impregnated material through a heater at about 95 to 120 C. for about 7 seconds, and reacting with the liquor an organic ester which hydrolyses slowly, being substantially completely "United States Patent hydrolysed approximately over the period of heating of the material.

In further accordance with the invention, we provide animal fibres, or yarns or fabrics containing the same, when dyed by any method set forth in the preceding paragraphs.

As an example of the hydrolysis, boiling aqueous caustic soda solution hydrolyses ethyl lactate with liberation of ethyl alcohol and lactic acid.

The rate of hydrolysis of the ester is important, because if it is too slow the alkali will not be neutralised quickly enough; while if too rapid the alkali in the dye liquor will be neutralised too quickly thereby interfering with the proper fixation of the dyestulf in the fabric. The quantity of ester used influences the rate at which the products of hydrolysis are formed; the optimum quantity is that amount of ester which when hydrolysed neutralises the whole of the alkali in the liquor adsorbed by the fabric.

In one method used in conjunction with the continuous method of dyeing of British Patent No. 620,584 aforesaid, vat or sulphur dye liquors are made up by adding to cold water the dyestufi, caustic soda, sodium hydrosulphite and other auxiliaries, and finally the organic ester. The cold .dye liquor may be used immediately or stored at room temperature (18 C.) for two or three hours. When required for use the cold dye liquor is pumped to the dye-bath through a pre-heater which raises the temperature of the dye liquor to C. within a few seconds before its absorption by the fabric.

Wool fabric passing through this dye-bath and thence through a bath of molten metal having a temperature of C. is immersed in the dye-bath for 0.44 second and in the molten metal for 6.7 seconds. The dyeing operation commences when the fabric enters the dye-bath. The dye liquor is absorbed by the fabric on passage of the latter through the dye-bath, and the dyestuff in the fabric is absorbed by the fibres of the fabric and fixed therein on passage of the fabric through the molten metal, the dyeing operation being completed on emergence of the fabric from the molten metal. It is found that the caustic soda remains at full strength sufficiently long to allow the liquor, in which the dyestuffs are dissolved, to be absorbed by the fabric, and thereafter the strength of the caustic soda in the fibres of the fabric is gradually reduced by hydrolysis of the ester with consequent reduced damage to the wool.

In another method used in conjunction with the continuous method of dyeing of British Patent No. 620,584 aforesaid, vat or sulphur dye liquors are made up by adding to cold water the dyestuff, caustic soda, sodium hydrosulphite and other auxiliaries. The cold dye liquor may be used immediately or stored for two to three hours. When required for use the cold dye liquor is pumped to the dye-bath through a preheater which raises the temperature to 75 C. Woollen fabric is impregnated with a solution of an organic ester, dried, and the impregnated fabric passed through the dye-bath and thence through a bath of molten metal having a temperature of 95 C. The fabric is immersed in the dyebath for 0.44 second and in the molten metal for 6.7 seconds. Esters suitable for this method have a low vapour pressure and high boiling point so that they remain in the wool fabric on drying out the moisture or solvent. As aforesaid, they should be easily hydrolysed by the aqueous caustic solution.

In yet another method used in conjunction .with the continuous method of dyeing of British Patent NoI 620,5 84 aforesaid, woollen fabric is first padded through a pigment vat liquor containing the ester and is then dried and developed by passage through a caustic-hydrosulphite liquor which replaces the dye liquor in the dye-path of the previous methods.

Patented Get. 23, i956 following examples are quoted:

mple J.---Dry scoured woollen fabric is preheated by passing through a hot air chamber and is then passed through a dye liquor which floats on the surface of molten metal alloy contained in a U-shaped vessel with limbs five feet deep. The dye liquor has the following composition:

The

The dye liquor is made up and stored at room temperature (18 C.) as required, and is pumped to the surface of the molten metal through a dye preheater,

.which heats the dye liquor to 75 C. within a few seconds before its absorption by the fabric. Fabric with a temperature of 75 C. passes through the dye liquor (depth eight inches) directly into molten metal alloy which has the following composition:

Percent Bismuth 50 Lead 26.7

Tin 13.3

Cadmium 10 The temperature of the alloy is 95 C. The fabric is immersed in the dye-bath for 0.44 second and in the alloy for 6.7 seconds and leaves the metal alloy through a 10% aqueous solution of Glaubers salt which floats on the exit surface with a temperature of 95 C. The

"supply of dye liquor to the surface of the metal, the dye temperature and the temperature of the alloy are all automatically controlled. Fabric emerging from the Glaubers salt bath passes into a conventional open width soaping range for oxidising, rinsing and soaping in known manner, and is coloured the fast green associated with this dyestuff.

Example 2.Wool-cotton union fabric containing 50% cotton, 50%- Wool, is dyed by impregnating with dye liquor in a two-bowl padding mangle with a dye-box of small capacity, and is thereafter passed through molten metal alloy contained in the U-shaped vessel of Example 1. The dry scoured fabric approaches the dye liquor by passing over steam-heated cylinders which ensure that the fabric enters the dye with a temperature of 80 C. The dye liquor has the following composition:

50 grn1s./ litre of the vat dye 1:2 anthraquinone naphthaacridone (C. I. 1162) supplied by I. C. I. Ltd., as Caledon Red ENS.

5 ccs./litre Alcopol T (Allied Colloids Ltd.).

5 grms./litre sodium hydroxide.

30 grms./ litre sodium silicate.

grms./litre sodium hydrosulphite.

5 grms./ litre glucose.

12 cos/litre normal propyl acetate.

The dye liquor is made up and stored at room temperature and fed, as required, to the box of the padder through a dye heater which raises the temperature of the dye to 75 C. just prior to its absorption by the fabric. The volume of dye liquor in the pad-box is small (one and a half gallons) and the nip is adjusted to give a fabric containing its own weight of dye liquor. The distance between the padder and the molten alloy surface is small to limit atmospheric effects and loss of temperature. The alloy has the composition shown in Example 1 and is maintained at 95 C. The fabric is immersed in the alloy for 6.7 seconds and leaves by Way of an aqueous Glaubers salt solution which floats on the exit surface as in Example 1. It passes into an open width continuous soaper for oxidation and washing in known manner.

In the foregoing Examples 1 and 2, hydrolysis of the n-propyl acetate commences on heating of the dye liquor, and when the fabric leaves the alloy the hydrolysis is substantially complete. Thus the time taken for substantially complete hydrolysis of the n-propyl acetate is approximately 10 seconds. Therefore, in the foregoing Examplesl and 2 a suitable ester is one which in an aqueous caustic liquor shows no considerable amount of hydrolysis in 2 to 3 hours at room temperature, but which is substantially completely hydrolysed in 10 seconds at -95 C.

Example 3.Wool fabric is impregnated with an 8% aqueous solution of diethyl tartrate containing a suitable wetting agent such as 1% Alcopol T (Allied Colloids). It is squeezed and dried so that 6% of diethyl tartrate remains in the fabric. This fabric is then passed through a dye liquor which floats on the surface of molten metal alloy contained in a U-shaped vessel, as in Example 1. The dye liquor has the following composition:

100 grms./ litre of the vat dyestutf 4:8 dibenzoyl diamino 1:5 dihydroxy-anthraquinone supplied by I. C. 1. Ltd. as Caledon Brilliant Violet ZBS (Colour Index No. 1134).

15 grms./litre caustic soda.

30 grms./ litre sodium silicate.

10 grms/litre glucose.

22.5 grms./litre sodium hydrosulphite.

10 cos/litre Calsolene oil HS (I. C. I. Ltd.).

The molten metal bath and the supply of dye liquor thereto are as in Example 1. The fabric is immersed in the dye-bath for 0.44 second and in the alloy for 6.7 seconds and leaves the metal alloy through a 10% aqueous solution of Glaubers salt which floats on the exit surface with a temperature of C. The time taken for the dyeing operation is thus about 7 seconds. Hydrolysis of the ester commences on entry of the fabric into the dye-bath and continues until the fabric leaves the metal alloy, the hydrolysis then being complete. Thus, the time taken for complete hydrolysis of the ester is about 7 seconds so that the caustic alkali in the fabric is neutralised at about the same rate as that at which the dyeing occurs.

The treated fabric after oxidising and soaping in the normal manner is found to be coloured a deep violet shade.

Example 4.Scoured wool fabric is pigment padded" with the following vat dyestulf liquor:

50 grms./litre of the vat dyestuff Caledon Brown RS (I. C. I. Ltd.), Colour Index No. 1151.

80 grms./litre diethyl tartrate.

10 guns/litre Calsolene Oil H. S. (I. C. I. Ltd.)

The fabric is squeezed to leave 75% of liquor in the fabric, and dried. The dye-impregnated fabric is developed by passing through a preheated alkaline hydrosulphite liquor floating on the surface of molten metal in place of the dye liquor described in Example 3. Hydrolysis of the ester commences on entry of the fabric into the hydrosulphite liquor and continues until the fabric leaves the metal alloy, the hydrolysis then being complete. Thus the time taken for complete hydrolysis of the ester is about 7 seconds. The developing liquor has the following composition:

12 grms./litre caustic soda.

20 grms./litre sodium silicate.

9 grms./ litre glucose.

10 grms./litre Calsolene Oil H. S. (I. C. I. Ltd.) 18 grms./ litre sodium hydrosulphite.

The developed fabric is oxidised and soaped in the normal manner giving a fabric with a tan colour.

Example 5.-Wool fabric is impregnated in a padding machine with a solution in acetone of diethyl tartrate and 1% Alcopol T, and is then dried to leave about 7% diethyl tartrate in the dry fabric. The fabric is dyed in the manner described in Example 3 but using the following dye liquor:

80 grms./litre Indanthrene Red RK (C. I. 1162). 11 grms./litre caustic soda.

20 grms./litre sodium silicate (water glass).

8 grms./litre glucose syrup.

20 grms./litre Alcopol T.

10 grms./litre wetting agent.

16 grms./litre sodium hydrosulphite.

After oxidising and soaping the fabric is red.

Example 6.Wool fabric is impregnated in a padding machine with an aqueous solution containing 10% diethyl tartrate and 1% Alcopol T and dried to leave 7% of the ester in the dry fabric. This fabric is dyed according to the method described in Example 3, but using the following dye liquor:

30 grms./litre of the sulphur dye, Indocarbon Black C. L.

conc. (I. G.) (C. I. probably 970).

10 grms./litre caustic soda.

20 grms./litre sodium silicate.

20 grms./ litre Alcopol T.

10 grms./litre wetting agent.

20 grms./litre sodium hydrosulphite.

10 grms./litre glucose syrup.

After oxidising and soaping the fabric is coloured a full black.

An ester suitable for use in the foregoing Examples 3 -to 6 is one which under the conditions described therein is substantially completely hydrolysed in 7 seconds at 9095 C.

Example 7 .--Scoured wool serge fabric is impregnated in a two-bowl pad mangle with the following liquor at a temperature of 60 C.:

50 grms./litre Caledon Brown RS (I. C. I. Ltd. Colour Index No. 1151).

100 grms./litre diethyl tartrate.

10 guns/litre Calsolene Oil HS (I. C. I. Ltd.).

The fabric is dried in hot air and again impregnated in a two bowl pad with the following developing liquor at 40 C.:

grms./litre caustic soda. 10 grms./litre Calsolene Oil HS. 22.5 grms./litre sodium hydrosulphite.

The wet fabric from this impregnation is passed continuously directly into a hot oil bath at 120 C. After 7 seconds immersion in the oil the fabric is continuously rinsed, oxidized, rinsed and soaped in known manner to give a fast tan-dyed fabric.

Regarding the esters mentioned in the foregoing specification:

(a) Normal propyl acetate is more stable cold and is therefore added to the cold dye-bath (Examples 1 and 2 (b) Diethyl tartrate and ethyl lactate are not very stable in cold caustic solution and they are therefore used in the cases where the ester is applied to the fabric before contacts of the fabric with the alkaline liquor (Examples 3 to 7). Diethyl tartrate and ethyl lactate are substantially completely hydrolysed in 7 seconds at 120 C. and may therefore be used in a hot oil process involving heating of the impregnated fabric in hot oil at 120 C. for about 7 seconds. Moreover, diethyl tartrate and ethyl lactate are substantially completely hydrolysed in 25 seconds at 60 C. and may therefore be used in processes involving heating of the impregnated fabric for about 25 seconds at 60 C.

Isopropyl acetate, which is more stable cold, is substantially completely hydrolysed in about 1 minute at and may therefore be used as the ester in the treatment of the fabric by a steam-pad process involving heating of the impregnated fabric to 105 for a period of about 1 minute.

We claim:

1. A method of dyeing animal fibers in continuous fashion which comprises impregnating said fibers with a dyestuif selected from the group consisting of vat and sulphur dyestuffs, fixing said dyestuff upon said fibers by passing said fibers through an alkaline aqueous reducing liquor bath, removing the impregnated fibers containing entrained liquor from the bath and reacting with said entrained liquor at elevated temperature for a period of from 7 seconds to one minute an organic ester which is present and is being hydrolyzed by said alkaline reducing liquor to liberate acid to neutralize the alkali in the fibers, said organic ester being selected from the group consisting of ethyl lactate, normal propyl acetate, isopropyl acetate and diethyl tartrate while the liquor is fixing said dyestuff upon said fiber, at least the major amount of said neutralization occurring after the fibers are removed from the alkaline aqueous reducing liquor bath.

2. A method according to claim 1 in which said alkaline aqueous reducing liquor is strongly alkaline and applied at elevated temperatures, the fixing of the dyestufi upon the fibers and the neutralization of the alkali in said reducing liquor by the acid liberated by the hydrolysation of said organic ester being effected over substantially the same period.

3. A method according to claim 1 wherein the elevated temperature is between 60 and C. and said temperature is maintained by passing the impregnated fibers through a molten metal bath.

4. A method according to claim 1 wherein the elevated temperature is 120 C. and said temperature is maintained by passing the impregnated fibers through a hot oil bath.

References Cited in the file of this patent UNITED STATES PATENTS 1,148,966 Hebden Aug. 3, 1915 1,747,107 Niederhausern Feb. 11, 1930 2,521,485 Schoen Sept. 5, 1950 FOREIGN PATENTS 578,800 France July 12, 1924 620,584 Great Britain Mar. 28, 1949 OTHER REFERENCES Jour. Soc. Dyers and Col. for September 1950, pages 478 to 482 (article by Cheetham) 

1. A METHOD OF DYEING ANIMAL FIBERS IN CONTINUOUS FASHION WHICH COMPRISES IMPREGNATING SAID FIBERS WITH A DYESTUFF SELECTED FROM THE GROUP CONSISTING OF VAT AND SULPHUR DYESTUFFS, FIXING SAID DYESTUFF UPON SAID FIBERS BY PASSING SAID FIBERS THROUGH AN ALKALINE AQUEOUS REDUCING LIQUOR BATH, REMOVING THE IMPREGNATED FIBERS CONTAINING ENTRAINED LIQUOR FROM THE BATH AND REACTING WITH SAID ENTRAINED LIQUOR AT ELEVATED TEMPERATURE FOR A PERIOD OF FROM 7 SECONDS TO ONE MINUTE AN ORGANIC ESTER WHICH IS PRESENT AND IS BEING HYDROLYZED BY SAID ALKALINE REDUCING SAID ORGANIC ESTER BEING SELECTED FROM THE GROUP CONSISTING OF ETHYL LACTATE, NORMAL PROPYL ACETATE, ISOPROPYL ACETATE AND DIETHYL TARTRATE WHILE THE LIQUOR IS FIXING SAID DYESTUFF UPON SAID FIBER, AT LEAST THE MAJOR AMOUNT OF SAID NEUTRALIZATION OCCURRING AFTER THE FIBERS ARE REMOVED FROM THE ALKALINE AQUEOUS REDUCING LIQUOR BATH. 